1. Field of the Invention
The present invention relates to a side air bag device comprising a plurality of air bags which are accommodated in folded states in a side of a seat for an occupant and which are expanded by a gas generated by an inflator upon side collision of a vehicle to be deployed between an inner surface of a side of a vehicle compartment and the occupant.
2. Description of the Related Art
A conventional side air bag devices is known, for example, from U.S Pat. No. 5,464,246 and U.S. Pat. No. 6,349,964. An air bag in the side air bag device described in U.S Pat. No. 5,464,246 is formed into a cylindrical shape and adapted to be deployed to connect an upper end of a seat back and a front end of a seat cushion, thereby restraining an occupant's body from a side of the breast to a side of the waist. An air bag in the side air bag device described in U.S Pat. No. 6,349,964 is divided into upper and lower chambers so that an occupant is effectively restrained by setting the internal pressure in the upper chamber at a lower value and the internal pressure in the lower chamber at a higher value.
The side air bag device described in U.S Pat. No. 5,464,246 is provided in each seat and comprises the single air bag having a uniform internal pressure, and hence it is impossible to adjust a restraint force in such a manner that the hardness of the air bag can be varied in correspondence to each site of an occupant's body. On the other hand, the side air bag device described in U.S. Pat. No. 6,349,964 has the following problem: a difference in internal pressure is generated by setting different open areas of openings through which the gas flows from the inflator into the upper and lower chambers, but the internal pressure in the entire air bag eventually becomes uniform, because the two chambers communicate with each other.